Hi Everyone:


I recently upgraded my parking brake cable to stainless since the original had given all it had. When I mounted everything back together I noticed the brake light would remain on and my brake peddle was weaker than before I started the project. I decided to bleed the brakes and as I was doing this I didn't notice much pressure when my wife held the brake peddle down as I was loosening the the bleed valve.

I bleed all four wheels starting from the furthest to the closest and thought my worries were over -- NOT. My brake light remains on and the brake peddle isn't as firm as it was before I started the project. I suspect my master cylinder to be the problem and I was going to replace it if you agree with my approach.

Also, I called my local parts store and they have a master cylinder Cardone brand for $24.00, but it doesn't have the bleed valves like the one I have. I didn't know if that would make a difference??? Zip Corvette has the same one I have for $80.00.

Any help here will be greatly appreciated. Thanks in advance!!!

Al

1970 Corvette

 

For that price sounds like a rebuilt. You can get a new Cardone just a few buck more, much better.
I think NAPA still has new with bleeders available.

Don't throw the original away, you can always get it sleeved like the calipers, if numbers mean anything to you.

 

If the brake light is staying on all the time, it may be that the new parking brake cable isn't allowing the parking brake lever to go all the way down. You can check if the reason for the light being on is the parking brake or the hydraulic system by disconnecting the wire in the center of the distribution block. With that wire disconnected, if the light goes out, the problem is in the hydraulic system. If the light stays on then the problem is with the parking brake lever or switch.

 

i would check the proportioning valve also they have a tendancy to get stuck or get air trapped in them,especially if they are 30 plus years old.make sure you are opening the bleeder screws in the right order too.there are 2 bleeders on each caliper and you have to open them in a certain sequence or you will never get all the air out.

 

did you replace the cables or the brake lines?

 

Nope, I checked the parking brake lever and it's all the way down. I also removed the cover and the switch is totally depressed.

 

I replaced the parking brake cable with a stainless steel.

 

I didn't think of checking the proportion value -- that's interesting. Also, I wasn't aware of an order for opening the bleeder valves. On the front there is only a single bleed valve but in the rear there're two as you have indicated. Could you please tell me the correct order?

Also, I bought this car in July from a lady who's father had passed away and had inherited the car. She provided me with a shoe box full of parts receipts her father kept. Yesterday, while I was rummaging in the shoe box trying to find a receipt for a brake master cylinder I noticed that he had purchased a quart of silicone based brake fluid (DOT 5) and now I'm not sure if I have a bigger problem because I added DOT3

 

Thanks noonie for the NAPA tip. I picked one up today on my way home from work -- new $37.00.

Thanks, again!

 

if you mixed silicone with dot 3 you got a big mess.i would google or search how to fix it because years ago a guy working in our shop did the same thing and every part that held or contacted the fluid had to be replaced.it was on a ford 1 ton but was told by the dealer it screwed up everything.as for bleeding the brakes you start with the farthest wheel from the master and open the inner bleeder first then the outer,that way air gets pushed to the outer side of caliper.my vette or i thought all vettes with disc brakes had 2 bleeders due to the split body design.but i could be wrong.also make sure the bleeders are at the top of the caliper instead of the bottom,which can happen if you install the right caliper on the left side of the car and vice verse.

 

Thanks for the info. Unfortunately, I may never know if the previous owner use it or not. All I have is a receipt that shows that he purchased it. I'll bleed the brakes again as you suggested and pray that it solves my problem.

 

ONeill,

Drain some fluid from the MC and take it to a good mechanic, he/she will tell you if there are different fluids mixed. If so, drain it all out and flush the whole system with methylated spirits.

Do this anyway, as the ethylene glycol fluid is hygroscopic. That means it absorbs water from the atmosphere and if left alone, will rust your steel brake lines from the inside out. You won't see this until a line rusts through and half of your brakes don't work.

Others mean well, but there is no correct order for bleeding the brakes, except for the two bleeders in each rear caliper. Do the inside one first.

You should remove your existing MC and pull it apart to check for damage, either rust, grooves or failed seals. You can get the original MC sleeved with stainless steel if needed. With new rubbers and piston(s) if necessary, your MC will be as good as new and will still be "original" from the outside.

Ideally, you should pull the calipers apart and do the same if necessary. Then you should flush out the steel brake lines with metho and replace all four rubber hoses. When everything is re-attached, fill the MC with new DOT 3 or 4 (forget silicon) and let it gravity bleed for a few days, keeping the MC topped up.

You will not have to do much bleeding if you go this way.

Regards from Down Under.

aussiejohn

 

I am struggling here to understand how replacing your parking brake cable caused your master cylinder to go bad?

 

It didn't.
This has to fall into the "one more thing" rule.

 

as merc49 said it may be the proportioning valve.tap is lightly on it's mounting bolts and bleed again.i just went through this and exactly as you describe.(replaced all 4 calipers).good luck.

 

I agree. I was struggling with this as well, but I couldn't think of anything else being the cause of the problem. However, since reading some of the replies I believe the problem is that I didn't bleed the rear calipers correctly. I'm going to bleed them again as described by merc49 and see if that solves my problem. I will post the results as soon as I'm done. I hope to get this done in the next few days.

 

I agree. I'm going to bleed the brakes again and see if that solves the problem.

 

That's funny . I'll have to remember that rule.

 

Thank you aussiejohn. It's always good to hear from our friends down under.

 

I bleed the brakes and got all of what appeared to be air & rust out of the lines. My brake light no longer lights and I seem to have good mushy brakes. My brake peddle still seems to have a good deal of travel and I wasn't sure if that was normal???